Radio circuit and apparatus



June 28, 1932.

D. A. NICOSIA ET AL 1,865,036

RADIO CIRCUIT AND APPARATUS Filed March 16. 1927 2 Sheets-Sheet l +5 VOLTS June 28, 1932; D. A. NICOSIA ET AL 1,365,036

RADIO CIRCUIT AND APPARATUS Filed March 16. 1927 2 Sheets-Sheet 2 WMHWHIHHHmm"... F7

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A T TORNE YJ' Patented June 28, 1932 DAVID A. NICOSIA AND HARRY SIPPEL, OF'GHICAGO, ILLINOIS RADIO CIRCUIT AND APPARATUS Application filed March '16, 1927. Serial No. 175,659.

This invention relates to a radio circuit and apparatus for use in radio receiving sets which is of such construction that sharp tuning may be effected and wherein feedback I or regeneration and resulting undesirable oscillation is minimized or prevented.

It is an important object of this invention to provide an improved circuit wherein means for opposing the well-known feed back effect of the output circuit on the input circuit comprises a bridge embodying concentrated adjusted impedances of high values connecting the grids of the thermionic valves with the antenna.

It is a further important object of this in vention to provide an inductance of such form that end capacity is minimized and at the same time, high magnetic efiiciency is assured.

closures in the specification and the accompanying drawings. I

The invention in a preferred form is shown on the drawings and hereinafter more fully described.

On the drawings: Figure 1 is a wiring diagram of a radio receiving circuit embodying the principles of the present invention.

Figure 2 is a view similar to Figure 1 sh owing a slight modification of the circuit.

Figure 3 is a fragmentary side elevation of the improved variable inductance used in connection wtih the circuit of this invention. Figure 4 is an end elevation taken along the line IVIV of Figure 3.

Figure 5 is an elevational view taken along the line IV--IV of Figure 3.

Figure 5 is an elevational view taken along the line V-V of Figure 3.

Figure 6 is a front elevation of one of the tuning dials. t Figure 7 is a fragmentary detail showing the method of winding the coil affording the It is finally an important object of this in-' variable inductance shown in Figures 3 and 4.

Figure 8 is an enlarged perspective view showing the arrangement of the improved variable inductance shown in Figure 4.

Figure 9 is a diagrammatic side elevation illustrating the flow of magnetic lines of force in the improved inductance embodied in the present invention.

Figure 10 isa diagrammatic view showing a development of the inductance illustrated in Figure 8.

Figure 11 is aside elevation showing a modified form of inductance embodying the present invention. I

Figure 12 is a view similar to Figure 10 showing a development of the inductance illustrated in Figure 11.

Figure 18 is a view similar to Figure 9 with reference to the inductance shown in Figure 11.

Figure 14 is a side elevation illustrating another modification of the inductance embodying the principles of the present in-, vention.

Figure 15 is a view similar to Figure 13 with reference to the inductance shown in. Figure 14.

Figure16 is a broken away View showing a form of condenser which may be used to provide the variable adjusted capacity employed in the antenna bridge forming a part of the present invention.

.As shown on the drawings:

The reference numeral 1 indicates an aerial or antenna of usual construction which is inductively coupled to a tuned radio frequency amplifying circuit embodying thermionic valves 3, 4 and 5 respectively, the output from said circuit in turnbeing inductively coupled to a suitable detector valve 6 in the usual manner either through additional stag-es of audio frequency amplification or directly to a loud speaker or similar device 7.

The present invention contemplates im- 5 proved means for preventing undesirable feed back and resulting oscillation which is normally present in circuits of this character and comprises a bridge between the grids of the thermionic valves 3,4 and 5 and the antenna 1, said bridge being connected to the antenna at a point in advance of its connection to the primary 8 of a usual coupling transformer. The bridge above mentioned comprises parallel variable adjusted condensers 9, 10 and 11 which are respectively connected to the grids of the thermionic valves 3, 4 and 5 and which in turn are connected respectively through series variable resistances 9, 10 and 11 with the antenna at the point heretofore mentioned. These resistances 9 10 and 11 are of high value, being perhaps in the neighborhood of 200,000 ohms each and are ordinarily only adjusted for the characteristics of the particular circuit, the variable condensers 9, 10 and 11 being similarly only adjusted to the characteristics of the circuit and not subsequently adjusted.

The form of variable condenser which may be conveniently used to afford the variable adjusted capacities 9, 10 and 11 is shown in Figure 16 and comprises a base 12 which is provided with terminals 13 and 14 and which supports an outer metallic cylinder 15, a dielectric 16, and a vertically adjustable inner metallic member 17. The inner metallic member 17 is internally threaded and supported by a screw 18 So that rotation of said member 17 relative to said screw effects a vertical movement of the inner metallic member 17 and consequently varies the capacity afforded by the condenser. The inner metallic member 17 is connected with the terminal 14 through the screw 18 and the outer metallic member is connected with the terminal 13.

In Figure 2, we have illustrated a slight modification of the circuit embodying the principles of the present invention wherein the variable capacities 9, 10 and 11 are connected with the grids of the aforementioned valves 3, 4 and 5 in the manner described in the circuit illustrated in Figure 1 but wherein variable high value resistances 9 10 and 11 are connected to said capacities in parallel with each other and to the antenna 1 through a common conductor 19. It will be seen that in this circuit the impedance to the feed back or oscillation is not cumulative as in the circuit shown in'Figure 1 but is individual to each thermionic valve, thus permitting of a somewhat more delicate initial calibration and being somewhat more eflicient, although we have found the circuit illustrated in Figure 1 to operate with a high degree of satisfaction in most instances.

This invention further provides an improved inductance for use in tuning the same comprising in its preferred form a toroidal formed coil 20 which gradually decreases in axial diameter from the filament terminal to the grid terminal. A form of coil embodying this construction is shown in Figures 5 to 9 inclusive, of the drawings, and comprises a conductor 21 wound about a suitable support 22 preferably of insulating material, the support being so arranged that the small end of the coil is brought adjacent the large end of the coil, the normal magnetic field about the axis being substantially as indicated by the dotted lines in Figure 9. By using a toroidal formed coil, magnetic leakage and interference is to a large extent eliminated but in the use of toroidal coils of a constant axial diameter, difficulty has been experienced with end capacity and also with the undesirable feature of the resonance points of a large number of the short wave lengths occurring close together near the grid end of the coil. By providing a coil of the form which we have invented, this end capacity from the grid to the filament is greatly reduced and the short wave length resonance points at the grid end of the coil are spaced farther apart along the axis of the coil thus facilitating tuning and the selection of short wave length stations, the wave lengths of which may be somewhat close together.

The improved coil embodying the present invention may be conveniently mounted on a suitable support 23 which in addition to supporting the coil afiords a bearing for a shaft 24 which carries a contact member 25 normally held in contact with the end turns of the coil 20 by means of a spring 26 engaged between the support 23 and an axle 27 on the shaft 24. Said shaft 24 is also journalcd in a suitable panel 28 and has a handle 29 with a pointer 30 cooperating with a dial 31 secured to its outer end outside said panel 28. Co-axial with the shaft 24 and secured to the inner face of the panel 28 is a toothed annulus 32 and secured to the shaft 24 is a locking pawl 33 which is adapted to be held in engagement with said toothed annulus when the contact member 25 is in adjusted position. This construction provides in effect a lockable adjustment which may be released by pushing in on the knob 29 to release the locking pawl 30 and the contact member 25 to permit the shaft and the contact member 25 to be turned. When the contact member 25 is moved to the desired adjusted position, the handle or knob 29 is released whereupon the spring serves to lock these parts in an adjusted position with the contact member 25 engaging the proper end turn of the coil 20 and the locking pawl 33 looking between the proper teeth in the annulus 32.

While the form of coil illustrated in Figures 5 to 10 inclusive, has proven to be the mostdesirable form, it is obvious that 1 other forms of coils embodying the present invention might be employed which would approximate the results which we attain through the use of the coil herein described. For example, in Figures 11 to 13 inclusive, we

have shown a form of coil which is separated in into two parts, each of which are of constantly decreasing axial diameter from the filament connection 34 to the grid connection 35. The flow of the magnetic lines of force in a coil of this type is illustrated in Figure 13, a development being shown in Figure 12, and it will be obvious that this form of coil achieves some of the desirable results of the toroidal form of coil and at the same time eliminates excess end capacity.

A coil such as illustrated in Figure 1 1 and 15 may also be employed in the circuit of this invention, it being noted that this coil essentially comprises two parts 36 and 37 respectively, of large and small axial diameter, the part 36 being connected to the filament terminal at 38 and the small part 37 being connected to the grid terminal at 39, the flow of the magnetic lines of force in this type of coil is diagrammatically shown in Figure 15.

It will be obvious that this invention provides a radio circuit and apparatus wherein undesirable feed back or regeneration effects are prevented by the antenna bridge embodying high value impedances consisting of the condensers 9 and the resistances 9 or condensers 9 and the resistances 9 connected in the manner heretofore described. These high value impedances are made adjustable so that they may be calibrated to the desired value, and once calibrated for the particular circuit for which they are used, the desired results are attained thereby in a superior manner.

The improved coil which we have provided assures sharp tuning and in the preferred form, the magnetic losses and interference are exceedingly low.

We are aware that many changes may be made and numerous details of construction may be varied through a Wide range without departing from the principles of this invention, and we therefore do not purpose limiting the patent granted hereon, otherwise than necessitated by the prior art.

lVe claim as our invention:

1. In a radio circuit, an antenna, a tuned amplifying circuit including parallel thermionic valves connected to said antenna, and parallel impedances of high value connected to the grids of said thermionic valves and to the antenna at a point in advance of its connection to said amplifying circuit.

2. In a radio circuit, an antenna, a tuned amplifying circuit including parallel thermionic valves connected to said antenna, and parallel impedances of high value each including a variable condenser connected to the grids of said thermionic valves and to the antenna at a point in advance of its connection to said amplifying circuit. 7

3. Ina radio circuit, an antenna, a tuned amplifying circuit including parallel thermionic valves connected to said antenna, parallel impedances of high value connected to the grids of said thermionic valves and to the antenna at a point in advance of its connection to said amplifying circuit, and toroidal transformer coils connected in the input circuit of each of said thermionic valves.

4. In a'radio circuit, an antenna, a tuned amplifying circuit including parallel thermionic valves connected to said antenna, parallel impedances of high value connected to the grids of said thermionic valves and to the antenna at a point in advance of its connection to said amplifying circuit, and variable toroidal coils connected in the input circuit of each of said thermionic valves.

5. In a radio circuit, an antenna, a tuned amplifying circuit including parallel thermionic valves connected to said antenna, parallel impedances of high value connected to the grids of said thermionic valves and to the antenna at a point in advance of its connection to said amplifying circuit, and toroidal coils of constantly decreasing axial diameter from the filament terminal to the grid terminal connected in the input circuit of each of said thermionic valves.

6. In a radio circuit, a thermionic valve including a grid and a filament, and a toroidal inductance connected between said grid and said filament, said inductance being of constantly increasing axial diameter from the grid connection to the filament connection thereof.

7 In a radio circuit, a thermionic valve including a grid and a filament, a variable toroidal inductance connected between said grid and said filament, said inductance being of constantly increasing axial diameter from the grid connection to the filament connection thereof.

8. In a radio circuit, an antenna, a tuned amplifying circuit including a thermionic valve connected to the said antenna, and a resistor in series with a condenser connected to the grid of the said thermionic valve and to the antenna at a point in advance of its connection to the said amplifying circuit.

9. In a radio circuit, a multi-electrode thermionic valve, a toroidal inductance connected between the grid and filament electrodes of said valve, said inductance being of constantly increasing axial diameter from the grid terminal to the filament terminal, a condenser, the said condenser being connected in shunt with the said toroidalinductance, and switch means in series circuit association with the said condenser and the said inductance to vary the amount of inductance shunted by the said condenser.

In witness whereof, we have hereunto subscribed our names at Chicago, county of Cook and State of Illinois.

HARRY SIPPEL. DAVID A. NIGOSIA. 

